As this type of apparatus, there has been suggested an apparatus which operates or calculates a tire steer angle midpoint (e.g. refer to Patent document 1). According to an electric power steering apparatus disclosed in the Patent document 1, a straight-travel state of the vehicle is accurately determined on the basis of a steering wheel angle, a vehicle speed, and a rack bar axial force. Thus, even if steering torque is applied such that a driver returns a steering wheel to a neutral position due to a deviated tire steer angle midpoint, a control tire steer angle midpoint can be accurately determined as a point of reference for detecting a rotation angle of a steering shaft.
Moreover, Patent document 2 discloses a technology of automatic driving of the vehicle along a target trajectory, as a technology to which this type of apparatus can be applied.